When a performance evaluator program is used, either to determine the costs of a given request or to evaluate the optimum system for the intended type of use (examples: fixed application, fixed DBMS, fixed operating system), it is necessary to parametrize a library containing the characteristics of the architecture of the system for which evaluation is to be done. In thus defining the architecture, the user is presented with a problem in determining whether the architecture is classified as a distributed model or a shared memory model. This classification has repercussions on the evaluation method used.